Dying Stars

White dwarfs are the dying remnants of stars like our sun. They are slowly cooling because the energy they radiate into space in the form of photons and neutrinos from the star's surface and core is no longer replenished by internal nuclear reactions. Denis Sullivan, at Victoria University, is using a 1m-telescope at the Mt John Observatory to observe white dwarfs to study how stars decay, but also as a method of verifying the existence of the neutrino-based mechanisms within their core.

White dwarfs were first identified as unusual stellar objects in the early part of last century. Their luminosity, temperature and mass implied that they were compact objects, very dense and with high surface gravities, and internal matter at extremely high pressures and temperatures. During the 1930s, relativity theory helped to determine that all stars that have a mass similar to that of our sun - which applies to 98 percent of all stars - turn into white dwarfs at the end of their lives. More massive stars either form neutron stars or supernovas when they die.

Native Frogs and Chytrid Disease

This month marks the end of the Year of the Frog, intended to draw attention to the conservation plight of frogs worldwide. At least half of the world's amphibian species are threatened with extinction. Habitat destruction is a major threat to many frog species, but more recently a deadly disease has been causing widespread extinctions. Unfortunately, chytrid disease has already reached New Zealand, and is posing a real threat to our four ancient endemic frog species.

Zoologist Phil Bishop, from the University of Otago, has been involved in studying the disease in Archey's frogs, a species that is already ranked as highly endangered. As well as investigating possible cures for the disease, he is investigating metabolic bone disease which is a problem in captive amphibians and reptiles worldwide, and is making it difficult to establish a captive breeding population of Archey's frog.

Fossil Crater

A maar crater inland from Dunedin was formed by a volcanic explosion about 23 million years ago, and probably filled up with water very quickly. The lake had no outlets and experienced very little disturbance - hence the layers of sediment are still intact and contain some of the best preserved fossils in New Zealand.

Among the fossils are complete fish and insects and leaves of several plants, including a fern which now only exists on the Three Kings islands and in some Northland forests, several leaves that haven't been found anywhere else in New Zealand, and two examples of orchids, which are the only organically preserved specimens worldwide.

University of Otago palaeontologist Daphne Lee and her colleagues, geologist Jon Lindqvist and plant taxonomist Jennifer Bannister (pictured on the left), say the forests around the lake were similar to those found in Thailand today, suggesting that Otago experienced a much warmer climate back then, during a period known to geologists as the Oligocene.